Proliferation of vascular endothelium occurs in response to both inflammatory and neoplastic stimuli but the factors responsible for endothelial growth under these conditions remains poorly understood. The present study is being undertaken to gain further insight into the mechanism of vascular proliferation as it occurs in response to inflammatory and neoplastic stimuli, and to examine the role that such an interrelationship might play in the control of tumor growth. Initial studies will involve an autoradiographic analysis of 3H-thymidine (3H-T) incorporation by endothelial cells at sites of 9-10 dimethyl, 1-2 benzanthracine (DMBA) induced hamster cheek pouch tumors, to determine the time-sequence and magnitude of endothelial replication during the development of malignant epithelial tumors and to correlate these findings with the time-course, distribution, magnitude and character of inflammatory cell infiltration at sites of tumor development. Subsequent studies will entail a direct and systematic examination of the angiogenic potential of malignant cheek pouch epithelium at various stages during its malignant transformation and the ability of various inflammatory cell types and media conditioned by these cells grown in culture to modulate neovascular response induced by malignant epithelium in the avascular cornea of the guinea pig eye. Solid tumor fragments and tumor cell suspension, alone and in combination with inflammatory cells (from normal and tumor-bearing hamsters) and products released by these cells in culture will be introduced intracorneally and neovascular responses will be assessed by observing the ingrowth of vascular sprouts from the limbus toward the depot of test materials in the cornea.